Vehicles having open topped bed such as pickup trucks and the like provide a versatile means for transporting and storing a variety of goods. The disadvantage of an open topped bed is that it is exposed to the elements. It has long been recognized as desirable to provide a cover for the bed of such vehicles to prevent the intrusion of rain and snow and protect goods being transported or stored in the vehicle. Many different covers have been invented to satisfy this need. The following patents are known to relate to covers and cover attachment systems for pickup beds:
U.S. Pat. No. 3,727,972-Belk PA0 U.S. Pat. No. 3,857,601-Robbins PA0 U.S. Pat. No. 4,036,521-Clenet PA0 U.S. Pat. No. 4,252,362-Campbell PA0 U.S. Pat. No. 4,273,377-Alexander PA0 U.S. Pat. No. 4,479,677-Gulette et al. PA0 U.S. Pat. No. 4,573,730-Gondert et al. PA0 U.S. Pat. No. 4,639,033-Wheatley PA0 U.S. Pat. No. 4,709,956-Bowman PA0 U.S. Pat. No. 4,730,866-Nett PA0 U.S. Pat. No. 4,792,179-Stevens PA0 U.S. Pat. No. 4,792,178-Kokx PA0 U.S. Pat. No. 4,838,602-Nett PA0 U.S. Pat. No. 4,861,092-Bogard PA0 U.S. Pat. No. 4,833,305-Horton PA0 U.S. Pat. No. 4,979,776-Schweickert PA0 U.S. Pat. No. 4,991,640-Verkindt et al. PA0 U.S. Pat. No. 5,058,652-Wheatley et al.
Cargo bed covers can be divided into two general categories: the rigid canopy and the flexible cover. The rigid canopy is generally made of fiberglass, plywood or some other durable rigid material. While such canopies have become widely accepted, they have certain drawbacks in that they are heavy and therefore difficult to install and remove. Once installed on a vehicle they are rarely removed. Rigid canopies therefore limit the carrying capacity of a vehicle on which they are installed. Articles taller than the distance between the bed and the top wall of the canopy cannot be transported. Rigid canopies also limit the load access to the vehicle since goods can only be loaded through the rear of the canopy.
It is therefore desirable to have a flexible cover which can be removed or collapsed as the need arises. Flexible covers include tonneau covers, a flat flexible cover attached to a perimeter of the top edge of the cargo bed, and flexible canopies which may or may not be collapsible.
The attachment of a flexible cover to a pickup bed is recognized as a difficult engineering exercise. Manufacturing tolerances permit variations in the size of pickup beds, which variations must be compensated for by the attachment system. In addition, the dimensions of a pickup bed change slightly with fluctuations in temperature, as do the dimensions of a flexible cover for the pickup bed. A good attachment system must therefore compensate for such variations so that the cover for the pickup bed remains taut under a variety of conditions which change with time. The covers must also be securely fastened, especially covers for vehicles used in the northern regions where snow accumulations are common. Snow loads can exert significant loads on a cargo bed cover and the attachment system must be able to resist those loads without damaging the cover or attachments.
Many tonneau covers are attached to pickup beds using snap or button fasteners that are affixed directly to the sidewalls of the pickup bed. Such attachment systems have certain drawbacks. Snap fasteners tend to freeze and/or corrode and the resultant stress induced when removing the cover can damage it. Button fasteners, while more reliable, may provide a path for the intrusion of water into the bed and the grommets required in the cover form weak points which tend to tear under stress. In addition, unless snap or button fasteners are affixed to adjustable rails, such fasteners provide no means of compensating for fluctuation in the dimensions of the box or of the cover as a result of temperature changes and/or aging of the cover fabric.
Furthermore, attachments which require the drilling of holes in a vehicle depreciate the value of the vehicle and accelerate corrosion. It is desirable to provide an attachment for a flexible cover which obviates a requirement for piercing the vehicle body. Such systems have been invented and generally comprise a rail which is clamped or glued to the sidewalls of the pickup bed. Some rails include an outwardly extending edge for receiving a J-shaped fastener, or for engaging a bight formed by a strip sewn along an edge of the cover. A system of the first type is taught by Wheatley et al. in U.S. Pat. Nos. 4,639,033 and 5,058,652. A system of the second type is taught by Stevens in U.S. Pat. No. 4,792,179.
Wheatley et al. teaches a mounting system for a tonneau cover which uses a J-shaped extruded fastener that is sewn along the edge of the cover for fastening it to outwardly extending longitudinal edges of rails clamped on the vehicle sidewalls. The J-shaped fasteners is said to compensate for dimensional changes in the cover due to temperature fluctuations or manufacturing tolerances, etc. One disadvantage of this system is that the stress on the cover is concentrated at the seams which affix the cover to the fastener. In addition, the J-shaped fastener is designed to unfurl under tension to compensate for variations in distance between tile cargo box sidewalls, and variations in the flexibility of the cover. It is assumed that under significant load, such as snow load, the cover could unfurl from the rail and collapse into the bed of the vehicle.
Stevens teaches a flexible truck bed cover which is attached to the truck bed by means of a plastic strip sewn onto the cover so that a sewn edge of the strip is adjacent an edge of the cover and a free edge of the strip is spaced inwardly from the edge of the cover. The plastic strip fits inside a gap at the top of the bed created between an attachment rail and a supporting frame or a bed liner. A disadvantage of this system is that pressure on the cover is applied directly to the seam which attaches the plastic strip to the cover. The attachment rail acts as a wedge which acts to separate the cover from the plastic strip. Although increased tension on the cover, such as snow load, tends to lock the cover more firmly in it's attachment to the truck bed, increased pressure tends to damage the cover because of pressure on the seam.
It is therefore apparent that there still exists a need for an attachment system which securely yet removably attaches a cover to the vehicle while compensating for dimensional changes and minimizing points of stress and wear.
There also exists a need for an attractive, lightweight, reliable, collapsible canopy for a pickup bed. Horton in U.S. Pat. No. 4,833,305 discloses a collapsible canopy for pickup trucks which includes a pair of channel members for mounting on the top sidewalls of the pickup box, slide members for reciprocal movement in the channels and rigid stays affixed to the slide members for supporting a flexible canopy. The canopy is collapsed by sliding the rigid stays to a front of the pickup bed. This canopy has certain drawbacks. The channel members are difficult to keep clean, especially if materials such as earth or crushed rock are hauled. Accumulations of dirt and debris interfere with the reciprocal motion of the slide members and make operation of the canopy difficult. Besides, moving a rigid stay in parallel channels is generally difficult as one side or the other tends to jamb. A lack of a continuous attachment for the side edges of the canopy is also a disadvantage since snow and rain can be blown under the edges.
There exists a need for a collapsible canopy for a pickup bed which covers the entire bed, is substantially weathertight along all edges and readily collapses to permit free access to substantially the entire bed.